1. Field of the Invention
The present invention relates to a method of operating a system for providing hearing assistance to a user comprising capturing and processing audio signals by a transmission unit and transmitting the audio signals from the transmission unit via wireless audio link to a receiver unit; processing the received audio signals in the receiver unit; and stimulating the user's hearing by stimulating means worn at or in the user's ear, according to the audio signals from the receiver unit. The invention also relates to such a system.
2. Description of Related Art
Usually in such systems the wireless audio link is an FM radio link. The benefit of such systems is that sound captured by a remote microphone at the transmission unit can be presented at a high sound pressure level to the hearing of the user wearing the receiver unit at his ear(s).
According to one typical application of such wireless audio systems, the stimulating means is a loudspeaker which is part of the receiver unit or is connected thereto. Such systems are particularly helpful for being used in teaching e.g. (a) normal-hearing children suffering from auditory processing disorders (APD), (b) children suffering a unilateral loss (one dead ear), or (c) children with a mild hearing loss, wherein the teacher's voice is captured by the microphone of the transmission unit, and the corresponding audio signals are transmitted to and reproduced by the receiver unit worn by the child, so that the teacher's voice can be heard by the child at an enhanced level, in particular with respect to the background noise level prevailing in the classroom. It is well known that presentation of the teacher's voice at such enhanced level supports the child in listening to the teacher.
Usually in such systems the audio signals received by the receiver are amplified at a given constant gain for being reproduced by the output transducer. Such receiver unit has as a drawback that due to the constant gain the audio signals received from the remote microphone are amplified irrespective of whether they are desired by the user (e.g. if the teacher is silent there is no benefit to the user by receiving audio signals from the remote microphone, which then may consist primarily of noise).
According to another typical application of wireless audio systems the receiver unit is connected to or integrated into a hearing instrument, such as a hearing aid. The benefit of such systems is that the microphone of the hearing instrument can be supplemented or replaced by the remote microphone which produces audio signals which are transmitted wirelessly to the FM receiver and thus to the hearing instrument. FM systems have been standard equipment for children with hearing loss (wearing hearing aids) and deaf children (implanted with a cochlear implant) in educational settings for many years.
Hearing impaired adults are also increasingly using FM systems. They typically use a sophisticated transmitter which can (a) be pointed to the audiosource of interest (in e.g. cocktail parties, (b) put on a table (e.g. in a restaurant or a business meeting), or (c) put around the neck of a partner/speaker and receivers that are connected to or integrated into the hearing aids. Some transmitters even have an integrated Bluetooth module given the hearing impaired adult the possibility to connect wirelessly with devices such as cell phones, laptops etc.
The merit of wireless audio systems lies in the fact that a microphone placed a few inches from the mouth of a person speaking receives speech at a much higher level than one placed several feet away. This increase in speech level corresponds to an increase in signal-to-noise ratio (SNR) due to the direct wireless connection to the listener's amplification system. The resulting improvements of signal level and SNR in the listener's ear are recognized as the primary benefits of FM radio systems, as hearing-impaired individuals are at a significant disadvantage when processing signals with a poor acoustical SNR.
In order to provide versatile systems that cover many listening situations, modern FM systems provide several operating modes. The transmitter may e.g. have different microphone settings, a Bluetooth mode, or be connected to an external audio source such as a TV, MP3-player etc. and the receiver may offer a choice between getting the sound from: (1) the hearing instrument microphone alone, (2) the FM microphone alone, or (3) a combination of FM and hearing instrument microphones together.
Usually, most of the time the FM system is used in mode (3), i.e. the FM plus hearing instrument combination (often labeled “FM+M” or “FM+ENV” mode). This operating mode allows the listener to perceive the speaker's voice from the remote microphone with a good SNR while the integrated hearing instrument microphone allows to listener to also hear environmental sounds. This allows the user/listener to hear and monitor his own voice, as well as voices of other people or environmental noise, as long as the loudness balance between the FM signal and the signal coming from the hearing instrument microphone is properly adjusted. The so-called “FM advantage” measures the relative loudness of signals when both the FM signal and the hearing instrument microphone are active at the same time. As defined by the ASHA (American Speech-Language-Hearing Association 2002), FM advantage compares the levels of the FM signal and the local microphone signal when the speaker and the user of an FM system are spaced by a distance of two meters. In this example, the voice of the speaker will travel 30 cm to the input of the FM microphone at a level of approximately 80 dB-SPL, whereas only about 65 dB-SPL will remain of this original signal after traveling the 2 m distance to the microphone in the hearing instrument. The ASHA guidelines recommend that the FM signal should have a level 10 dB higher than the level of the hearing instrument's microphone signal at the output of the user's hearing instrument.
When following the ASHA guidelines (or any similar recommendation), the relative gain, i.e. the ratio of the gain applied to the audio signals produced by the FM microphone and the gain applied to the audio signals produced by the hearing instrument microphone, has to be set to a fixed value in order to achieve e.g. the recommended FM advantage of 10 dB under the above-mentioned specific conditions. Accordingly, heretofore—depending on the type of hearing instrument used—the audio output of the FM receiver has been adjusted in such a way that the desired FM advantage is either fixed or programmable by a professional, so that during use of the system the FM advantage—and hence the gain ratio—is constant in the FM+M mode of the FM receiver.
WO 02/23948 A1 relates to an example of such an FM receiver which not only receives audio signals from a remote microphone transmitter but in addition may communicate with remote devices such as a remote control or a programming unit via wireless link for data transmission.
EP 1 638 367 A2 relates to another example of an FM receiver for receiving audio signals from a remote microphone transmitter, wherein the FM receiver upon receipt of a polling signal from the remote microphone transmitter is capable of transmitting status information regarding the FM receiver to the remote microphone transmitter.
WO 97/21325 A1 relates to a hearing system comprising a remote unit with a microphone and an FM transmitter and an FM receiver connected to a hearing aid equipped with a microphone. The hearing aid can be operated in three modes, i.e. “hearing aid only”, “FM only” or “FM+M”. In the FM+M mode the maximum loudness of the hearing aid microphone audio signal is reduced by a fixed value between 1 and 10 dB below the maximum loudness of the FM microphone audio signal, for example by 4 dB. Both the FM microphone and the hearing aid microphone may be provided with an automatic gain control (AGC) unit.
Several scientific studies show that wireless hearing systems, such as FM systems, are extremely beneficial for hearing impaired persons. Yet, the market penetration for such systems, especially for hearing impaired adults, is by far not what one could expect. According to these studies, the main reason is the lack of appropriate counseling and training of the hearing-impaired person, so that the hearing-impaired user often is not able to utilize his wireless system in the most beneficial manner. On the other hand, the lack of counseling and training at least in part is due to a lack of information regarding how the system is used by the user.
US 2004/0190739 A1 relates to a method for recording information in a hearing device. As one example it is mentioned that the hearing device is a binaural hearing device consisting of two hearing device parts which are connected to each other via a wireless link, wherein the quality of the link is monitored and recorded as a function of time. For example, the link quality may be divided into three levels, with the present level being recorded as a function of time. Such procedure is known as “data logging”.
Another example of data logging in a hearing aid is described in EP 1 367 857 A1, according to which the values of operation parameters of a hearing aid as a function of time may be recorded in the hearing aid for being read-out through a data communication interface to a host computer. The hearing aid comprises at least two microphones and a T-coil. A similar system is described in U.S. Pat. No. 6,785,394 B1.
U.S. Pat. No. 6,741,712 B2 relates to a hearing aid which is similar to that of U.S. Pat. No. 6,785,394 B1 and wherein the use time of the hearing aid is accumulated and, when a given threshold is reached, a certain action will take place, for example, deactivation of the hearing aid, provision of an alarm signal, change of parameters and/or programs, etc.
US 2004/0190737 A1 relates to a hearing aid which may be binaural and which is capable of data logging by storing parameters and information, such as hardware data, information of the fitting history of the hearing aid, operating data or current adjustments or time signals, and statistical data, in a memory provided in the hearing aid. The hearing aid comprises a connecting unit for transferring the recorded data to an external device. The selection of the data to be recorded is freely programmable.
U.S. Pat. No. 4,972,487 relates to another example of a hearing aid with data logging capability, wherein information like the number of times control programs are changed, the number of times a given control program is selected, and the total time duration for which a given program is selected, are recorded and read by an external device.
As already explained contemporary FM transmitters are designed to be versatile and intended for use in various different listening environments. For example, the transmitter may have different audio processing capabilities, for example, different degrees of acoustic beam forming, an audio input, an auxiliary microphone input and a wireless interface (e.g. Bluetooth) for connection to a mobile phone.
Such versatility is necessary to accommodate the different listening situations. However, this adds complexity for the user and this implies that an optimum use of the equipment is only warranted if the user is appropriately counseled and trained. After such a counseling session, the user goes back to his home/work environment and then it is often very difficult to trace back how the system is actually used by him.
Also, in the case of hearing impaired children, it is important that the teachers and/or the parents use the equipment appropriately. Also, in this case it is often difficult to ascertain that the equipment is used optimally in a school environment.
It is an object of the invention to provide for a method of operating a wireless hearing assistance system, which allows for optimized counseling and training of the user and/or caretaker It is a further object of the invention to provide for a corresponding hearing assistance system.